1. Field of the Invention
This invention relates generally to semiconductor processing, and more particularly to interposers and methods of fabricating the same.
2. Description of the Related Art
Stacked semiconductor chip devices present a host of design and integration challenges for scientists and engineers. Common problems include providing adequate electrical interfaces between the stacked semiconductor chips themselves and between the individual chips and some type of circuit board, such as a motherboard or semiconductor chip package substrate, to which the semiconductor chips are mounted. Still another technical challenge associated with stacked semiconductor chips is testing.
Semiconductor interposers are sometimes used to serve as supporting and interconnect substrates for one or more semiconductor chips. A conventional semiconductor interposer consists of a silicon substrate and metallization to provide electrical pathways. The top side of the interposer typically includes conductor pads for connection to the solder bumps of the stacked chip(s). The bottom side typically includes conductor pads and solder bumps to connect the interposer to a circuit board of one sort or another.
A process flow to transform bare semiconductor wafers into collections of interposers and chips and then mount the semiconductor chips on those interposers, and in-turn the interposers on circuit boards, involves a large number of individual steps. In a conventional process, the photolithography steps to fabricate top side bump pads of interposers are performed using a stepper that consists of a reticle or set of reticles and a reduction lens. The stepper defines a reticle field of the top side. The conventional top side reticle field has a smaller footprint than the interposer. The portion of the interposer outside the reticle field is called an overhang. The overhang is unavailable for conductor pad and solder bump placement in conventional interposer fabrication. This limits the sizes and packing density of chips on conventional interposers.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.